Triple coil incandescent filament

Abstract

This invention relates to a single strand filament wire arranged into a triple-coil filament for an incandescent lamp. The triple-coil filament has selected dimensions that do not require recrystallization of the tungsten wire of the triple-coil filament prior to arranging the triple-coil filament within the incandescent lamp.

What we claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. An incandescent lamp comprising an electrically conductive base having a hermetically sealed light-transmissive envelope attached thereto, means for structurally and electrically mounting a filament within the said enclosure, a triple-coil filament electrically connected to and supported by said means for mounting, wherein said triple-coil filament comprises: a coiled-coiled-coil of tungsten wire having an outer diameter D3 in the range of 20d to 26d, where d is the diameter of the tungsten wire   said triple coil filament with the given range having a coil geometry that allows its successful arrangement within said incandescent lamp without sagging and without the need of prior recrystallization or stress-relieving treatment.   
     
     
       2. An incandescent lamp according to claim 1 wherein the outer diameter D3 has a preferred range of 24d to 26d. 
     
     
       3. An incandescent lamp according to claim 1 wherein said coiled-coiled-coil has a pitch ratio of greater than 1.9.